1. Field of the Invention
The invention relates to an optical device, and more particularly to a scanner lens.
2. Description of the Related Art
Scanners are generally classified into two categories, i.e. list-type and photographic-type scanners. Among the scanner types, the image pickup efficiency of the photographic-type scanners is better than that of the list-type scanners. Referring to FIG. 1, a conventional photographic-type scanner 1 comprises a main body 11, a scanner lens 12, a light source 13, and a plurality of reflective mirrors 15. The scanner lens 12 is disposed in the main body 11. Light from the light source 13 is output to a target 14 which needs to be scanned and is reflected thereby to the reflective mirrors 15 disposed in the main body 11. Then, the image of the target 14 is imaged on the scanner lens 12 by reflection of the reflective mirrors 15. Here, the scanner lens 12 provides a view angle of around 40°. When the view angle of the scanner lens 12 is not large enough (i.e. when the scanner lens 12 is provided with a long focal length), the width and height of the photographic-type scanner 1 are large. Accordingly, to reduce the size of the photographic-type scanner 1, the view angle of the scanner lens 12 must be increased.
Hence, there is a need for a scanner lens with an increased view angle.